John e



UNITED STATES PATENT OFFICE.

JOHN E. GENN, OF CHICAGO. ILLINOIS, ASSIGNOR T0 STEWART-WARNER SPEEDOMETER CORPORATION7 OF CHICAGO, ILLINOIS, A CORPORATION OF VIRGINIA.

SPARK-PLUG.

Application led August 15, 1918.

To all wlw/n, vt may Conce/rn:

lle it known that I, JouN E. GENN, a citizen of the United States, and a resident of the city of Chicago, in the county of Cook and the State of Illinois, have invented certain new and useful Improvements in Spark- Ilugs, of which the following `is a specification, reference being had to the accompanying drawings, forming a part thereof.

This invention relates to means for dissipating excess heat from a spark plug employed inan internal combustion engine, and isalso directed to a particular form of electrode especially adapted tol work well at high temperatures.. It consists in the features and elements hereinafter describedl` and shown in the drawings as indicated by the claims. -Y f In the drawings:

Figure 1 is an aXial section ofa spark plug` illustrating various details thereof embodying this invention.

Fig. 2 is a transverse section taken as indicated at line 2 2 on Fig. 1, for showing `the porcelain insulator'. Q.

the shape and mounting of the electrode which is a detail of the invention.

The spark plug illustrated in the drawing comprises the. usual metallic shell, 1, in which there is secured the porcelain insulator, 2, having its enlargement 3, clamped between the shoulder, 4, of the shell, 1., and a gland or bushing, screwed into the upper end of said shell with packing washers, G and 7, interposed. To assist in dissipating the eX- cessive. heat acquired by the shell, 1, from the adjacent.. parts of theengine cylinder, the shell may be grooved to formcooling tins or ribs` 8.

But additional capacit \v for carrying ofl:` excessive heat is provided in the construction of the conductor member. 9. connecting with the central electrode, 10, carried in This conductor, 9. is formed of a tube having a neck, 11, at its lower end engaged with the grooved upper end of the electrode. 10, by rolling or crimping the metal of said neck into the groove. 12, of the'electrode. By a similar expedient the central hub or neck, 13, of the metalli(l cap. 1l, is attached to the tube, 9, near its upper end. and the tube is longitudinally positioned in the bore of the porcelain. 2, h v crimping the edge of the flange, 15. into an exterior groove, 16, in the porcelain as shown. The bore in the por- Specication of Letters latent.

Patented Sept. 9, 1919.

serial No. 249.940

celain is made slightly larger than the exterior diameter of the tube, 9, and at the lower end the bore is slightly larger than the electrode, 10, to permit of rapid assembling, and the space thus formed is filled with cement, 17, which serves to secure the conductor, 9, and electrode, 10, firmly in position, and forms a gas tight joint between the parts.

A small quantity of mercury in liquid form indicated at 18 lis placed 1n the tube, 9, and since the,spark plug is practically alwaysused in upright or approximately upright. position this liquid mercury will flow to the lower end of` thetube adjacent the end of the electrode, 10, and in contact therewith. The upper end of the tube is then sealed by a screw plug, 19. As the electrode, 10. and the porcelain, 2, become heated, the mercury at 18 is vaporized and the vapor rises, finally filling the tube, 9, completely; but coming in contact with the upper portion which is open to the outer air, the vapor gives off its heat to the metal of the tube and `of the plug, 19, and is again condensed, whereupon it falls to the lower end of the tube in liquid form to repeat the operation. The drawing shows a spherical shell, 20, adapted to serve as a terminal for connection with suitably designed spring clips on the ends of the conductor Wire by which the ignition current is transmitted to the' spark plug. By perfor-ating this shell. 20, by a number of apertures, (21, to permit the circulation of air therethrough, it is lnade to serve as additional radiating surface for dissipating the heat transferred to the upper end of the tubular conductor, 9, and the screw plug, 19. It is evident, however. that any other form of terminal such as a binding nut on the end of the conductor could be specially designed lfor the purpose of heat radiation, and indeed the shell, 20, may be considered primarily as a radiator and only secondarilly as a con# ductor terminal and connecting member.

It is found Iby experiment that even if 'the mercury, 18, is entirely omitted from the tubular conductor, 9, the conductor itself will transmit a considerable quantit of heat from its lower end to its upper en and will radiate such heat more readily than if it were of solid construction. Being tubular instead of solid in cross-section, it has a much larger surface in proportion to the high temperature in the The disk is formed with a `perforated Yterminal much It will be understood that cross-sectional middle required for its function as an electrical conductor, and a portion of this area bein ell, 20, while other parts are in direct contact with said shell, it will be seen that quite effective radiation will be secured from this detail of construction alone. VYVVith the addition of the mercury at 18 the rapid dissipation of any undeslrable uantity of heat is assured.

It is we recognized that where both electrodes are formed of wire, particularly where the grounded electrode carried by the skirt of the shell, 1, is of Wire and bent to bring its point at the proper distance from the insulated electrode, 10, the effect of a combustion chamr 1s often to Warp said bent electrode out of shape, thus varying the spark gap from that intended, and seriously interfering with the proper operation of the plug.

preferable form of grounded electrode is shown in the drawings, comprising a flat disk, 22, of nickel or nickel allo'y having one edge comprisin a circular arc adapted to coincide with t e cylindrical wall of the skirt of the shell, 1, when the disk is inserted in a transverse slot cut in said wall. The disk being inserted in the slot, it is secured therein by staking,`tha't is, byforming the metal of the rim of the skirt by means of a center punch or similar tool, so as to indent the surface of the disk, 22, at the point, 23, and drive into the indentation a portion of the metal of the skirt, as indicated in Fig. 1.

hole at 24 adjacent the inner Wall of the skirt of the shell, l, and adapted to serve -as a drain aperture for any oil which mightbecome lodged on the upper surface of the disk, 22, and also to permit freer circulation of the gas about the electrode. As shown in Fig. 2, the curved edge, 25, of the disk, 22, coincides with the outer Wall of the skirt of the shell, While its straight edge, 26, formed upon a chord of the arc, 25, extends proximate to the electrode, 10, to form the spark gap. with an ignition current of relatively low intensit the spark will occur almost entirely at t e point of exposed within the closest approach between the two electrodes; but Wit l increasing intensity of the ignition current, the spark will tend to spread out along the edge, 26, of the disk, 22, thus distributing the wear on the disk and insuring a lon term of service therefor.

I c aim:

1. In a spark plug comprising an insulating member and an electrode carried therein, a conductor connected with said electrode within the insulator and heat radiating means at the outer end of the conductor comprising a metallic shell of approximately spherical form secured in contact with said conductor adapted to sewe as a connecting terminal therefor, and having its wall apertured to admit air to the inner surface of said Walls for increasing its capacity for radiating heat, transmitted from the conductor. Y*

2. In a spark plug comprising a metallic shell, an insulator mounted therein, and an electrode carried by said insulator, the shell terminating in a substantially cylindrical skirt surrounding said electrode and having a transverse slot cut in from one side thereof near the end and a second electrode to cooperate with the first, comprising a Hat disk secured in said transverse slot at one side only of the first electrode, an edge of said disk extending proximate to said first electrode but spaced therefrom to form a spark gap' 3. In a spark plug comprising a metallic shell, an insulator mounted therein, an electrode carried by said insulator, the shell terminating in a substantially cylindrical skirt surrounding said electrode, a flat metallic member having one edge curved to approximately coincide with the outer Wall of said skirt and another edge extending through the space between the first electrode and the inner Wall of said skirt proximate to said first electrode to form a spark gap, and an aperture in said flat electrode adjacent the inner wall of the skirt.

In testimony whereof, I have hereunto set `my hand at Chicago, Illinois, this 12th day of Aug., 1918.

J. E. GEN N. 

